Traditional Chinese Simplified Chinese

  • Can A Quiet Sun Halt Warming on Earth?

  • Wednesday, 19th August 2015

Whenever there are reports of predicted decrease in solar activity, climate change deniers will seize the opportunity to exaggerate the effect of the solar activity on the Earth's temperature change. An oft-quoted piece of misinformation spread by the deniers is the return of ice age due to weakening solar activity. So to what extent does the solar activity contribute to variations in the Earth's temperature?

Satellite-based instruments have been measuring the amount of solar energy reaching the top of the atmosphere (also known as total solar irradiance, or TSI in short) since the late 1970s. The average value of TSI is found to be about 1361 Wm-2. While solar activity follows a cycle of roughly 11 years, the average fluctuation of TSI over the past several solar cycles is only about 0.1%. For pre-satellite times, TSI variations have to be estimated from sunspot numbers or radioisotope analysis of polar ice and tree rings. Solar activity was very low during the period of 1645-1715, also known as the Maunder Minimum. The estimated difference in TSI values between the Maunder Minimum and the present day is also in the order of 0.1%.

As simulated by the US National Aeronautics and Space Administration (NASA) state-of-the-art climate model, changes in terms of global surface temperature anomaly due to solar activity were found to be generally within plus or minus 0.1oC over the period of 1880-2005 (blue line in Figure 1), a rather insignificant contribution as compared against the fast-growing influence of human-caused increase in greenhouse gases (red line in Figure 1). Similar conclusions were drawn in a recent climate model study conducted by the scientists at the UK Meteorological Office[1] to simulate conditions for the second half of the 21st century under the high greenhouse gas concentration scenario and incorporating a decreasing solar output down to the Maunder Minimum levels. It was found that the cooling effect arising from reduced solar output was a mere 0.1oC. To put this into context, we are talking about several degrees of temperature increase by the end of the 21st century under the high greenhouse gas concentration scenario according to projections (Figure 2) in the Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC). As such, to rely on the Sun to give us a helping hand appears to be just wishful thinking!

Figure 1

Figure 1      Simulated global surface temperature anomaly (relative to the 1880-1910 average)
due to solar activity and greenhouse gases. (data source: NASA)



Figure 2

Figure 2      Projected global average surface temperature change (relative to the average of 1986-2005) under
the high (in red) and low (in blue) greenhouse gas concentration scenarios in the 21st century,
with the colour-shaded regions indicating the respective range of uncertainty. (Source: IPCC)




S M Lee and F C Sham


Reference:

[1] Scientists show a decline in solar activity could not halt global warming
www.metoffice.gov.uk/news/releases/archive/2015/solar-activity


  • An Extraordinary Voyage - Exploratory Upper-air Sounding over the South China Sea (Part II)

  • Tuesday, 11th August 2015

...continued


2015.6.15    Fine becoming cloudy
After a day of cruising, the ship had reached southwest of Xisha, about 800 km from Hong Kong. Armed with experience from the previous two balloon launches, and with assistance from crew members, the launching work became smoother. We could finish up and send the data back to the Observatory within 3 hours every time. KC and I took turns to have breakfast and looked after the data reception. We could also spend some time to observe the cumulus clouds. They were cool with very sharp edges at the bottom parallel to the sea surface, like being chopped by a sharp knife (Figure 11).

Figure 11

Figure 11      A leisure moment on board to observe the clouds - Cumulus with rain shaft (left)
and sharp cloud edges at the bottom (right).


The sea state was better than we expected. The crew said that the weather and sea state would usually be the best from April to June in the South China Sea, with calm seas like a mirror. This is quite different from what we normally think of. We thought the southwest monsoon would be active in May and June, hence a wavy sea. We lost the chance for wave and swell watching, but fortunately we did not have to take sea-sick pills! The mobile phone rang at night, probably because there were oil-rigs nearby. It was signal from Vietnam. There was even a cold call from Hong Kong. Of course I would not answer as it was a roaming one!


2015.6.16    Cloudy with rain
As usual, when I got up in the morning, KC had everything ready. The ship already traveled to south of 10 N and west of 110 E, about 1500 km from Hong Kong. Mobile phone signal had totally lost. Radio noise was also dead, which meant this was the best time for launching radiosonde! It was cloudy today and there were heavy showers in the afternoon. The seas were moderate (Figure 12) but we hardly felt it on board. The experience gained at King's Park tells us that the balloon may burst earlier if it is raining. It is because moisture can stick onto the balloon surface and becomes ice when the balloon rises to upper atmosphere. The tension of the balloon may then be affected, leading to an early burst. This was proven again by the balloon launch on that night. The balloon passed through a thick layer of clouds (Figure 13, relative humidity reached 100% between 4 to 7 km height) and could not pass 100 hPa level, which was about 16 km high. This was the 'worst' launch during the whole voyage.

Figure 12

Figure 12      Waviest moment in the voyage with white horses.



Figure 13

Figure 13      Upper-air meteorological information on the night of 16 June. Balloon passed through
cloud layer at about 4-7 km high and burst at around 16 km height.



2015.6.17    Partly cloudy becoming fine
It was about 600 km from our destination, Singapore, in the early morning. KC and I prepared for the last balloon launch in the morning. There would be no further launch at night as the crew would be busy preparing for mooring when the ship headed closer to landmass. The weather turned better today. Twilight sneaked out from the cloud deck and crepuscular rays blessed the Earth from the cloud gaps (Figure 14). It was such a beautiful picture together with the waves generated by the ship. Launching a balloon became an enjoyable task and it was concluded almost perfectly. Following the Third Officer, we had a walk on the deck. It swept away all the dull feeling being stuck inside the cabin in the past few days. Of course we took the good opportunities to take photos down under the mast in the bow.

Figure 14

Figure 14      Twilight (left) and crepuscular rays (right).


The marine traffic had become busy after dinner. Ships were seen traversing orderly on the navigation radar. Though not far from Singapore, the crew was paying extra attention tonight. It was because an oil tanker was hijacked in nearby waters just a week ago and communication equipment on board was damaged. The tanker and the crew were all towed away (see related news). The crew ought to be in high alert when they were on duty for the "Pirate Shift". As pirates normally ride on speed boats and board the ship from the stern, the crew had to pay particular attention to the sound of speed boat engines. As told by the crew, oil tankers were the usual targets as they contained millions of US dollars of oil or diesel. The pirates would pump them away or ask for a ransom. Merchant ships, on the other hand, only have goods and they are too heavy to be taken away. That is why the pirates normally take the easier targets, namely the oil tankers.


2015.6.18    Fine
The ship entered the Singapore Strait slowly after midnight. The smell of pandan cake was in my dreams. I took the opportunity in the morning to thank Captain Duan with a set of the Observatory souvenir stamps for his great hospitality and assistance during the past few days (Figure 15). With the assistance from the local agent, we passed the customs and immigration and entered Singapore. That concluded the amazing 6-night / 5-day balloon launching voyage.

Figure 15

Figure 15      The author (left) thanked Captain Duan Shaoda (right) for his support of the exploratory launch.


We are now analyzing the data obtained during this voyage to see if there are any potential benefits to weather forecasting. In any case, if upper-air sounding can be made over the South China Sea, it should assist typhoon prediction and also contribute positively to the navigation safety on the "One Road" [2].

Last but not least, we would like to express our sincere gratitude to Orient Overseas Container Line Ltd. for their full support. Special thanks go to Captain Duan Shaoda and his team for their kind assistance and endurance. Also big thanks to the cook for the delicious meals so that we did not feel home-sick on board!



David Lam


Note:

[2] "One Road" means 21st Century Maritime Silk Road in the "One Belt One Road" initiative.


  • An Extraordinary Voyage - Exploratory Upper-air Sounding over the South China Sea (Part I)

  • Friday, 7th August 2015

The Observatory carries out upper-air sounding at 8 a.m. and 8 p.m. (i.e. 00 UTC and 12 UTC) every day by launching balloons carrying radiosonde from the automatic upper-air sounding system at King's Park Meteorological Station. In late 2014, the Observatory acquired a portable sounding system to explore the feasibility of conducting upper-air sounding operation elsewhere from King's Park to support operational and research needs. One of the ideas is to make sounding operation over the South China Sea. Back in the 1970's, the Observatory participated in a global weather experiment and had launched sounding balloons on board of ships. Sounding balloons were launched on a British warship and a merchant ship to collect meteorological data over the South China Sea (Figure 1)

Figure 1

Figure 1      The Observatory launched upper-air sounding balloons over the South China Sea in the 1970s.


After some 30 years, KC (Fung Kwok-chu, Senior Scientific Assistant) and I were excited to start our week-long historical mission on board of M.V. OOCL Busan [1] on the night of 12 June 2015. The destination was Singapore (Figure 2). Below is the excerpt from the journey diary:


Figure 2

Figure 2      The voyage from Hong Kong to Singapore and the 7 sounding balloon launching locations.



2015.6.12    Fine
In the afternoon, I felt a bit excited after knowing the ship had already arrived in Hong Kong. After dinner, I said goodnight and goodbye to the kids. KC and I then went to Kwai Chung Container Terminal and boarded M.V. OOCL Busan (Figure 3) after going through some immigration formalities. Ah Chow (Chow Chi-hung, Senior Scientific Assistant) also went on board to help checking the gears. In case something were found missing, he could rush back to King's Park and fetch them. After boarding, we asked the crew right away if the instruments and tools had been delivered on board and we then checked if they were functioning normally. The radio was quite noisy in the Terminal and the reception was barely acceptable. We believed that the condition should improve in the open seas. On the deck, we said goodbye to Ah Chow who went down the ship ladder and left the Terminal near midnight.

Figure 3

Figure 3      Picture of M.V. OOCL Busan.



2015.6.13    Fine
We were briefed about the escape and safety measures on board before leaving Hong Kong waters. Following a crew member, we got the chance to take a look at the engine room to feel the heat stress there. The ship stopped by Shekou Port first (Figure 4). The marine pilots from both the Hong Kong and the mainland sides took turns to lead us to the Port. During the few hours in Shekou, KC took the time to do some final checks of the portable system (Figure 5), getting ready for the first balloon of M.V. OOCL Busan on next morning. The ship left Shekou at around 10 p.m. It passed through the busy Urmston Road, Kap Shui Mun, East Lamma Channel, and left Hong Kong waters near Po Toi.

Figure 4

Figure 4      Container ship on route to Shekou Port on calm seas.



Figure 5

Figure 5       Adjusting the antennas of the portable sounding system.



2015.6.14    Fine
It was already 6 a.m. when I got up. The ship was about 200 km southwest of Hong Kong. Mobile phone signal had been lost for long. It was time to test out how we could survive without mobile phone and the Internet! KC seemed to be very keen expecting for the first launch. He was ready and had connected all the instruments at the bridge before 6:30 a.m. Though we were far away from landmass, there were still plenty of radio noises. It took us some time before we finally located a useable frequency and locked the radiosonde signal. Then KC proceeded to inflate the balloon at the bridge wing (Figure 6)

Figure 6

Figure 6      Inflating the balloon with helium gas.


The ship headed to the southwest with a cruising speed of about 16 knots. The winds near sea surface were over 10 knots, also from the southwest. The resultant winds were reaching gale force! Though KC is an expert for launching balloons, he still found it difficult to inflate and tie the balloon under near Signal No.8 wind conditions. The balloon turned into crescent shape under strong winds (Figure 7). Having seen that, the crew came over and helped out, not only to feel the fun of launching a balloon, but also to learn about the difficulties of our work.

Figure 7

Figure 7      Balloon in crescent shape under strong winds.


Without further ado, the balloon was released and the radiosonde flew quickly away. I then rushed back to the bridge to check if the data were sent back to the receiver. The hard work paid off and the data were successfully received. The whole process took about three and a half hours to complete. The 1st balloon of M.V. OOCL Busan was considered a success. Captain Duan Shaoda came over and congratulated us. However, the work was not completed yet. We still had to send the data back to the forecasters in the Observatory for their reference. Without optic fibers on the ship, the only way is to use Captain's exclusive email to send the data files as attachments via satellite transmission back to Hong Kong. Though it was Sunday, the Observatory operates 7/24 and colleagues in the forecasting office were waiting for this "1st balloon". Forecasters compared the data from the 1st balloon with that collected from King's Park regular launch (Figure 8). The relative humidity profile aloft was quite different although M.V. OOCL Busan and King's Park were only 200 km apart.

Figure 8

Figure 8      Upper-air meteorological data from the first sounding balloon of M.V. OOCL Busan (left) and King's Park
Meteorological Station (right) (8 a.m. HKT on 14 June 2015).


It was almost 6:30 p.m. after the siesta. The dinner was a BBQ party on the deck. I must say it was equivalent to the Captain's Dinner of luxury cruises, only without formal attires. It was our honour to dine with the Captain at the same table. Too bad KC and I needed to leave early, as we had to launch balloon at 8 p.m. (i.e. 12 UTC).

With some experience gained from the morning launch, we thought it would be easier this time. It was already dark and we had to pay extra caution. The radiosonde preparation work was smooth. Inflating and tying the balloon were easy jobs for KC. However, it was only 'the lull before the storm'. The winds tonight were not weaker than those in the morning. Given that we have so little experience in launching balloon on a ship, we were simply too confident about the launch. When we released the balloon, it crashed to the crane on board and burst in a split second. The radiosonde plummeted into the sea. The crew came over and checked us out. We were lucky that no instruments on board were damaged. While reflecting on what had happened and learning from the experience, we decided to take time and launch another balloon. This time Captain Duan suggested steering the ship a bit so that the sailing direction (the ship was heading southwest) would deviate from the wind direction (also from the southwest) by a small angle such that the balloon would not crash to the instruments on board (Figure 9). This method really worked and the balloon flew out smoothly (Figure 10). Captain Duan had made such a wise move and we used this method for every launch thereafter and the balloon releases were all very smooth!

Figure 9

Figure 9      Cruising route (white dotted line) as shown on the navigation radar of M.V. OOCL Busan.
Captain Duan steered the ship a little leading to a smooth balloon launch.



Figure 10

Figure 10      Capturing the moment when the balloon flied out smoothly as the sailing direction
of the ship changed a little.


The sky was not pith dark on that night. It was full of brilliant stars. I had never seen so many stars in my life, even more than those observed in Sai Kung, Southern District, Lantau South, or anywhere in foreign countries without much light pollution. Tens of thousands of stars and the visible Milky Way made me feel small. Too bad I do not know much about photography and I only had my mobile phone and a handycam with me. I was not able to record the spectacular scene, but that certainly left a remarkable impression in my memory.


To be continued ...



David Lam


Note:

[1] "M.V. OOCL Busan" is one of the members of the Hong Kong Volunteer Observing Ships Scheme.